基于RS与GIS的九寨沟国家级自然保护区地震前后植被覆盖度变化分析

Analysis of Vegetation Coverage Change in Jiuzhaigou National Nature Reserve Before and After Earthquake Based on RS and GIS

为探究九寨沟国家级自然保护区在地震前后植被覆盖度变化的范围及程度,本研究基于ENVI5.3及ArcGIS 10.2软件,利用地震前后遥感影像数据,提取并计算归一化植被指数(NDVI)与植被覆盖度(Fractional Vegetation Cover,FVC)数据,基于归一化植被指数与植被覆盖度数据分析九寨沟国家级自然保护区在2017年7.0级地震前后植被覆盖度的时空变化。结果表明:(1)九寨沟国家级自然保护区植被覆盖度在地震后明显下降,主要集中在保护区北部、中部及西南部;(2)震中位于保护区核心区,地震后,核心区低植被覆盖面积增幅最大;(3)地震对海拔<4000 m的区域植被影响较大,对海拔>4000 m的区域内植被影响较小;植被在坡度25°~35°区间,坡向为东坡、东南坡、南坡和西南坡的区域减少的面积较多。研究结果将为九寨沟自然保护区震后生态修复与重建提供一定的科学参考,同时帮助我们深入理解地震对不同地形因子的植被覆盖度的影响机制与变化规律。

In order to explore the range and degree of vegetation coverage change in Jiuzhaigou National Nature Reserve before and after the earthquake,based on ENVI 5.3 and ArcGIS 10.2 software platform,this study extracted and calculated normalized vegetation index(NDVI)and vegetation coverage(FVC)data by using remote sensing image data before and after the earthquake,and then analyzed the temporal and spatial pattern changes of vegetation coverage in Jiuzhaigou National Nature Reserve before and after the magnitude 7.0 earthquake in 2017.The results showed that:(1)The vegetation coverage of Jiuzhaigou National Nature Reserve decreased significantly after the earthquake,mainly concentrated in the north,middle and southwest of the reserve;(2)The epicenter was located in the core area of the reserve.After the earthquake,the increase of low vegetation coverage in the core area was the largest.(3)The earthquake had a great impact on the vegetation in the area with an altitude of<4000 m,but had little impact on the vegetation in the area with an altitude of>4000 m.The earthquake reduced the area of vegetation in the slope range of 25°~35°,and the slope directions were east slope,southeast slope,south slope and southwest slope.The research results will provide some scientific reference for the ecological restoration and reconstruction of Jiuzhaigou Nature Reserve after the earthquake,and help us deeply understand the influence mechanism and change law of the earthquake on the vegetation coverage of different topographic factors.